The present invention relates to electrical voltage transformers. More specifically, but without limitation thereto, the present invention relates to a dielectric power transformer for low-loss power conversion at frequencies beyond around 2 MHZ.
Current digital logic circuits operate at lower voltages and must attenuate higher frequency voltage transients than circuits of earlier designs. Suitable power supplies for the newer digital circuits may operate in the range of 2-100 MHZ. However, current approaches are limited by the properties of magnetic transformers. Magnetic transformers become inefficient beyond around 2 MHZ because current magnetic core materials tend to be too lossy at the higher frequencies, and because leakage inductance increases with frequency as the cube of the frequency. Nonmagnetic core transformers may be used to reduce power losses, but nonmagnetic core transformers exhibit voltage droop with changes in the load due to insufficient coupling of the primary to the secondary.
An example of a transformer suitable for nonmagnetic cores is U.S. Pat. No. 4,274,046 by Harrison. This transformer comprises a series of pi-type or T-type sections. A disadvantage of this approach is that multiple inductors are required for the several pi or T sections. Another disadvantage is that a short circuit in the load results in a zero input impedance to the power source.
A need therefore exists for a power transformer that is efficient at higher frequencies in the range of about 2-100 MHZ.